I really, really try to not get suckered by Internet ads, like those preying on prurient interests in sex, violence, catastrophe, and cute cats. But I couldn’t help myself, and checked out the Top Ten Best Cartoons; the top two are SpongeBob Square Pants and The Simpsons, according to this list, and Loony Tunes is number three (I would have voted numero uno.) This Top Ten website got me thinking, is there a list for the best “sludge metal bands,” as I have always found the naming of this music genre ironical? Indeed, they do! The Best Sludge Metal Bands? are Mastadon and Melvins (one reviewer’s comments on the Melvins was “A unique sound to sludge metal, it’s almost like really evil grunge music that's really heavy it somehow became metal.” Got it?!)

WowI I see in these TOP TWO PAPERS a connection to top topics in biosolids: phosphorus and biochar. Many, many problems with biosolids would be fixed, at least in the minds of our critics, if we got rid of phosphorus and if we converted biosolids to biochar.

The sad fact is that these two papers float to the top for the very reason they are in a cauldron of controversy.

Dr. Sharpley’s review article is sobering. The phosphorus issue is seemingly intractable, policies and programs are insufficient, and all sources need to be managed, biosolids included, or especially. He writes: “Terrestrial P legacies encompass prior nutrient and land management activities that have built up soil P to levels that exceed crop requirements and modified the connectivity between terrestrial P sources and fluvial transport.”

Land applied biosolids is part of the “terrestrial P legacy.” Dr. Herschell Elliott framed this issue at the MABA Biosolids Symposium last November. In Will Phosphorus Scuttle Land Application of Biosolids? Dr. Elliot pointed out that an application of biosolids to meet a corn crop nitrogen requirement added 600 pounds per acre of P2O5. Under the Maryland rule governing farming activities with a low P loss potential sites, the more favorable management class, the total allowable P addition in biosolids should not be greater than that quantity needed for 3 years of crop uptake, or 45 pounds in each of three years. The phosphorus limitation of biosolids application would be about 1/5 the nitrogen application requirements. This is too small for practicable application operations.

Dr. Elliott recommended, in addition to our professions engagement with the makers of the rules, that we pursue two actions: “Recovery of wastewater P and transporting biosolids to targeted P deficient areas.” Let’s see what that would take!

Despite these reference facilities, the path to P extraction and to achieving a balance of N and P in biosolids is not clear. If you are seriously interested in P extraction, go immediately to Phosphorus recovery from wastewater: Recovery potential, heavy metal depollution and costs,because the full document is open access and is thorough in its evaluation tools: “This work compares 19 relevant P recovery technologies by considering their relationships with existing wastewater and sludge treatment systems,” using a “Material Flow Assessment” that underscores the complexity of the chemistry and calculations. The bottom-line: ”an ideal recovery technology cannot be presented.” None of the 19 technologies could show a significant rebalancing of N and P.

To this academic exercise, I would recommend two great case studies of technology evaluation. A Comprehensive Evaluation of Struvite Control at the EBMUD Main Wastewater Treatment Plant, illustrating a thorough review of technology options, concluded “enhanced cleaning (of the struvite) provided the most cost-effective alternative.” At the 2017 WEF Residuals and Biosolids Conference, Denver Metro reported on its trials with AirPrex, “Pilot-scale Evaluation of AirPrex® for Digestate Treatment.” While the balancing of nutrients was listed as one of 5 drivers in the trial, the results actually resulted in increased phosphorus concentrations in the biosolids.

The second Top Two JEQ paper dealt with pyrolysis and biochar. Strangely enough, pyrolysis and biochar enjoys support among anti-biosolids activists, and this is a strong reason to take a careful look. Yet, it attracts what I term pseudo specialists. In the biosolids-sensitized British Columbia province, Graeme Bethel, of Pivotal Integrated Resource Management, has publicly presented on the merits of advanced thermal processes for sludge treatment, linking himself to the Woodland (California) Research and with a Dr. Matt Summers of WestBiofuels. Kevin Hull, CEO of Emergent Waste Solution, has spoken at public meetings about how his Advanced Pyrolysis system is an alternative to land spreading. A quick scan of Google, Bing and LinkedIn uncover no reference facilities or even credible demonstrations. The potential is still to be proven.

Along with the conceptual appeal of pyrolysis comes the “irrational exuberance” for its output, biochar. The 2016 award paper, Characterization of Slow Pyrolysis Biochars: Effects of Feedstocks and Pyrolysis Temperature on Biochar Properties, actually is a sober evaluation that biochar “may be suitable for soil application by contributing to the nutrient status and adding recalcitrant C to the soil but also potentially pose ecotoxicological challenges.” This caution is reflected also in the USDA publication Carefully unraveling the intricacies of biochar: “even though there’s already a lot of public enthusiasm about using biochar in agricultural production, ARS scientists are much more cautious about the possibilities.” One reason is that real-world results have been negative. But you wouldn’t know this by the crowded field of new experts, e.g., Biochar Consulting (Canada) which “provides comprehensive technical services to clients who wish to undertake projects to produce or utilize Biocarbon or ‘Biochar’.”

Yet the door is not closed to either pyrolysis or biochar as beneficial technologies for biosolids in the future. There are some positive research reports: Biochar production by sewage sludge pyrolysis concluded “Pyrolysis suppressed heavy metal release for the non-impregnated biochars, indicating that there is no environmental risk using sludge-derived biochars as soil amendments.” Yet other research reveals it is a tricky area. In Pyrolysis methods impact biosolids-derived biochar composition, maize growth and nutrition, the authors reported growth inhibition: “an incubation or weathering period may be necessary to limit potential short-term, phytotoxic effects.” Not only is pyrolysis tough, but operating pyrolysis in a way that produces a biochar beneficial to soil is even tougher.

Dr. Sohi’s work makes for a most interesting connection, tying together pyrolysis, biochar and phosphorus. Dr. Sohi is one of the authors of Biochar and enhanced phosphate capture: Mapping mechanisms to functional properties which examines “biochar materials derived from secondary organic resources and aimed at sustainable recovery and re-use of wastewater phosphorus (P).” Here the concept is pyrolyzing high Fe residuals, thereby producing a “tailored” biochar that could capture dissolved inorganic P from wastewater effluents. Pyrolyzed biosolids capturing P from wastewater, what a concept!

Oh, geez! What happens to the spent P-enriched biochar? If you don’t landfill it, then I guess you land spread it. Then we return to Dr. Elliott’s suggestion, “transporting biosolids to targeted P deficient areas.” Sounds easy? Not! And, we are back where we started.

At the end of the day we have the TOP TWO issues: massive build-up of pollutant nutrients in coastal urban areas and widespread degradation of soil resources. Biosolids can help solve both, and it can do so in its Class B, low cost form, but for disjointed programs, policies and priorities that interfere with biosolids use in P deficient areas. What we need is for biosolids to RECLAIM THE TOP SPOT